If you are running out of space on your Windows machine, you can reclaim disk space by purging your system shadow copies. Shadow copies are more common on Windows Vista and Windows 7 machines, so you can try this to save a few gigabyte of space.
Originally posted by Amit Agarwal of Labnol.Org
Step 1: Disk nearly full? Free-up some space..
Click the Windows Start button and type cmd in the search box (not the Run dialog). Now press Ctrl + Shift + Enter to open the command prompt with Administrator privileges. Click Yes if you are shown the User Access Control Window.
Now type the following command to remove only the old shadow copies:
c:>vssadmin delete shadows /for=c: /oldest
Or, if your system is working normally, use this command to remove all the shadow copies.
c:>vssadmin delete shadows /for=c: /all
Refer to Microsoft Technet for more details on the VssAdmin command.
Step 2: Why reserve less space for shadow copies..
Windows will continue to save new restore points until all the reserved disk space is filled up. That means if you have less reserved space, the old ones will get deleted more quickly as new ones are created.
Go to Windows Start –> Run and type sysdm.cpl to open the System Properties dialog. Click the “System Protection” tab and choose Configure.
If the disk space allocated for system protection is on the higher side, you may move the “Max Usage” slider to the left and set it anywhere between 3% and 5% of the total disk size. The reserved space should also be greater than 300 MB according to Windows help.
Step 3: Make a fresh start..
Now that you have recovered some important space, go back to the “System Protection” tab and click Create to to capture of snapshot of your system in its current working state – just to be on the safe side of things.